Return Value of [NSString initWithFormat]

An NSString object initialized by using format as a template into which the remaining argument values are substituted according to the canonical locale. The returned object may be different from the original receiver.

Discussion of [NSString initWithFormat]

Invokes initWithFormat:locale:arguments: with nil as the locale, hence using the canonical locale to format numbers. This is useful, for example, if you want to produce "non-localized" formatting which needs to be written out to files and parsed back later.